/*
 * Copyright 2007 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 */
package gchisto.utils;

/**
 *
 * @author tony
 */
public class Refresher {

    private class Task implements WorkerTask {

        public void doIt() {
            callback.refresh();
            completeTask();
        }
    }
    final private WorkerThread workerThread;
    final private RefresherCallback callback;
    boolean inProgress = false;
    boolean pending = false;

    private void addTask() {
        inProgress = true;
        callback.beforeAddingTask();
        workerThread.add(new Task());
    }

    synchronized private void completeTask() {
        if (pending) {
            addTask();
            pending = false;
        } else {
            inProgress = false;
        }
    }

    public void possiblyRefresh() {
        if (!pending) {
            possiblyRefreshInternal();
        }
    }

    synchronized public void possiblyRefreshInternal() {
        if (callback.shouldRefresh()) {
            if (!inProgress) {
                addTask();
            } else {
                pending = true;
            }
        }
    }

    public Refresher(
            WorkerThread workerThread,
            RefresherCallback callback) {
        this.workerThread = workerThread;
        this.callback = callback;
    }
}
